The Clinical, Cognitive, and Analytical Core will provide management of human studies, maintenance of a shared database, and statistical oversight for Projects I, II, and III. These activities include recmiting, screening, consent and enrollment of study participants; coordinating scheduling laboratory tests, neurocognitive tests, transcranial Doppler ultrasonography and brain imaging; and database management and statistical analysis. Establishing these functions in a Core assures continuity of recruitment and procedures, cost savings, quality sample collection, and data processing.